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R1200RT intermitently running bad


dan cata

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Hi,

 

So I have this friend that owns a 2005 R1200RT. The bike has a very low mileage, ~ 34k kms. Like new.

 

The problem is that every now and then, the bike runs really bad, like just one cylinder running. I worked on the bike, did the valve adjustment, TB syncing, new plugs, new upper coils.

 

So the bike runs fine for 1000 kms, then, all of a sudden, it starts to run bad, idles roughly and when revved, like I said, it runs like only one cylinder is running...

 

I changed the fuel pump and no luck. I changed the fuel pump driver, the part on the tank with aluminum heat radiator, no luck.

 

Everything looks fine on the bike, no interventions on the wiring harness, no nothing. The GS911 shows something about the EWS, but that only intervenes on startup, AFAIK. And that error is intermittent so I get the poor running even when that error does not show up.

 

One thing that I noticed is that this is happening mostly when the tank is full, so I investigated around that area. I think I found the issue, but I need a confirmation...

 

On the L/H side of the tank, there is the pump unit, that has 2 wire connectors, 2 thick hoses for gas and one smaller tube, for venting purposes if you ask me. The nipple where the small rubber tube goes was corroded, rusted, clogged all the way. I opened it up, cleaned it and filled the tank all the way and now it looks like it works fine.

 

My question is where does that hose go and if you all agree that this was the issue with the bike. My guess is that it allows air in as the gas level decreases and since it was clogged, the fuel pump could not deliver. Let the bike sit overnight, pressure decreased and everything worked fine.

 

PS it is not the water drain from the filler hole as that small hose goes on the R/H side of the tank, as you sit.

 

I guess I am talking about #10 - breather line :)

 

http://www.realoem.com/bmw/enUS/showparts?id=0387-USA-04-2005-K26-BMW-R_900_RT_05_SF_0367,0387_&diagId=16_0717

 

 

Dan.

 

 

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I wonder if the canister could be causing the problem?

 

If the bike is in Romania, it probably doesn't have a canister (that's strictly a U.S. thing, as far as I'm aware).

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That is exactly the behavior you would expect if the tank vent hose is plugged -- the bike runs ok until enough vacuum has built up in the tank (from the fuel pump sucking gas out), until the pump can no longer overcome the vacuum and line pressure drops.

 

If your friend can drive until the tank needs to be refilled (without opening the cap until the refill) without the problem showing back up, you fixed the problem.

 

*If* the problem recurs, see whether opening the fuel cap fixes it -- opening the cap vents the tank, "resetting" it so the pump can do its job. If that is the case, you'll need to follow the vent hose up to the top of the tank and verify it is open.

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On the L/H side of the tank, there is the pump unit, that has 2 wire connectors, 2 thick hoses for gas and one smaller tube, for venting purposes if you ask me. The nipple where the small rubber tube goes was corroded, rusted, clogged all the way. I opened it up, cleaned it and filled the tank all the way and now it looks like it works fine.

 

My question is where does that hose go and if you all agree that this was the issue with the bike. My guess is that it allows air in as the gas level decreases and since it was clogged, the fuel pump could not deliver. Let the bike sit overnight, pressure decreased and everything worked fine.

 

Afternoon Dan

 

That IS the filler cap ring water drain. That small metal nipple passes the water out from a small hose that runs from the filler cap ring THROUGH the inside of the tank then out through the pump pass through then on to the L/H side under the bike.

 

The actual tank vent is on top of tank & forward/right.

 

I hope you figure it out but have my doubts that opening that water drain nipple will have any effect.

 

I have yet to find a 1200RT that a plugged tank vent stops the engine or causes poor running as the fuel pump in INSIDE the tank so it isn't restricted by max vacuum possible, it is only effected by it's max output pressure & tank construction.

 

Those 1200RT tanks are thin plastic with lots of odd shapes so when the tank vent plugs the 50 psi+ pump just sucks the sides on that thin plastic tank inward to allow it to keep fuel flowing out. (I have seen them sucked in with the wing almost sucked flat)

 

 

 

 

 

 

 

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But I remember I blew on the hoses and when I blew on the one which I suspect to be the clogged one, it sounded like it came from somewhere inside the tank, and not the drain hole in the filler.

 

Also, if you check the link above, it says there "10 fuel tank breather line"

That line goes trough the inside the tank somewhere else, not sure where.

 

On the other hand, what you say also makes sense, the vent line to be in the upper most side of the tank, like you say. But where does my line go then?

 

Dan.

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Afternoon Dan

 

Your line runs from the little hole in the fill cap ring, to a short hose inside the tank, then to that small metal nipple that runs through the fuel pump pass through, then out a small diameter hose that goes to just behind the riders L/H (shifter side) foot peg (look up in there & you should see it)

 

1200RT%20fuel%20tank_zpsqhnbqqjw.jpg

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And I was so happy thinking I found the problem :)

Now I will not be able to sleep tonight... again :D

 

Dan.

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Something else comes trough my mind... could it be that the tilt mechanism gets stuck, resulting in the same void as the initial hypothesis? I will try and open that up today and see how it looks.

 

Dan.

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Morning Dan

 

 

Possible but not likely, just look at those large plastic wings in the picture above, air doesn't really have to get in until the last gallon or so remaining as the tank plastic just sucks in as the fuel is pumped out.

 

Remember the pump is in the tank so it isn't trying to suck fuel out of the tank with only 29" Hg of vacuum (or less), it is trying to push fuel out of the tank with 50 psi+ of pressure.

 

Even IF you do have a tank venting problem I seriously doubt it is in the roll over valve, way more likely to be a problem in the vent hose or Evap Canister (if that bike has one).

 

You might check it out with mechanics--

 

Just remove bike tupperware (so you can view fuel tank) , then unplug one fuel injector plastic fuel line, then place a hose (or tube) over the open fuel injector plastic line, then put a container under that hose (or tube), then jump the fuel pump to 12 volts.

 

Now just pump a gallon or two out of the tank while watching the plastic fuel tank.

 

If the tank starts to suck in, or crush like a soda can, then you have tank venting issues.

 

On the other hand-- if it will easily pump out a couple of gallons of fuel then your basic problem isn't from tank venting.

 

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